Birds' feathers or plumage, are some of the most amazing variable animal characteristics that can be observed by the naked eye. The patterns that we see in birds' feathers are made up of complex combinations of mottles, scales, bars, and spots. But, how are these colours and patterns made?

Dr Ismael Galvan and his expert research team from the University of Chicago, US studied the plumage coloration in 9,000 bird species to see what types of pigments were present in its complex feather patterns.Plumage coloration mainly happens courtesy of two types of pigments: melanins, which produce a range of black, grey, brown, and orange colours, and carotenoids, which are used by specialized feather structures to generate brighter colour hues.

The study is published in the journal Physiological and Biochemical Zoology.Birds cannot produce carotenoids on their own. For feathers with bright colours, birds must consume food items that contain these pigments, and the carotenoids circulate through the bloodstream and to the feather follicles. Birds' bodies do not have direct cellular control of synthesizing and depositing carotenoids; nor do they have control of the specialized feather structures, which react to the consumed carotenoids with a mechanism that is not regulated by specialized cells.